Electronic scanning antennas



'' Nov. 11, 1969 R. TRIGON 3,478,358

ELECTRONIC SCANNING ANTENNAS Filed Nov. 29, 1966 P/ldS' swrrms MEMORY COMPUTER United States Patent 3,478,358 ELECTRONIC SCANNING ANTENNAS Roland Trigon, Paris, France, assignor to CSFCompagnie Generale de Telegraphie Sans Fil, a corporation of France Filed Nov. 29, 1966, Ser. No. 597,801 Claims priority, applicatiozn9 France, Nov. 30, 1965,

Int. Cl. rro4b 7/02 U.S. Cl. 343-100 1 Claim ABSTRACT OF THE DISCLOSURE The present invention relates to directive antennas of the type comprising a plurality of radiating sources and wherein the scanning of a given angle by the beam is produced by phase shifting said radiating sources with respect to each other.

To obtain a given deviation of the radiation direction of the antenna, it is known to phase shift each source with respect to the others by a value which, instead of being that exactly necessary, is an approximate value selected amongst a plurality of quantized levels. The direction of the systematic phase errors due to this quantization has hitherto been determined by rounding off each phase value of the nearest quantified value.

This method has the great disadvantage of giving, for certain frequencies and certain pointing angles of the beam, a periodical systematic error. This causes undesirable secondary lobes to appear in the radiation diagram of the antenna. The direction of these lobes depends on the period of the error and their levels depend on its amplitude. Assigning the sign to the phase error occurring for each source of an antenna with n sources if the actually selected phase value is higher than the desired value, and the sign in the opposite case, the direction of the systematic phase error for the whole antenna will be symbolized by a succession of n+ and signs. This succession defines therefore a function direction of the phase error which can present two different values corresponding respectively to the and signs. The direction and the level of the secondary lobes appearing in the radiation diagram of the antenna due to the phase quantization depend on the spectrum of the function direction of the phase error, which spectrum is the Fourier transform of this function. In the case of a periodical error, this spectrum presents at least two peaks which correspond to the appearance of at least two large secondary lobes.

It is an object of the invention to avoid this drawback by suitably selecting for each radiating source the direction in which the phase value is to be rounded off.

According to the invention, there is provided an electronic scanning antenna comprising: an array of a plurality of radiating sources; common energy supplying means for feeding said sources; a plurality of controlled phase shifting means respectively connected between said radiating sources and said common means for shifting the phase of said radiating sources by quantified amounts and having respective control inputs; computing means for computing the phase of each radiating source for a desired direction of the beam of said antenna and for dep 2 3,478,358 Patented Nov. 11, 1969 termining said quantified amounts, said computing means having data inputs a direction of the phase error input and a plurality of outputs respectively connected to said control inputs and memory means coupled to said last mentioned input for storing a code and for supplying to said computing means the direction of the phase error in the determination of each of said quantized amounts according to said code.

For a better understanding of the invention and to show how the same may be carried into effect, reference will be made to the drawing accompanying the following description and in which is shown an electronic scanning antenna embodying the invention.

The drawing shows an electronic scanning antenna, comprising an array of radiating sources a.r'.j., located on a surface or along a line, where i is an integer varying from 1 to p and j is an integer varying from 1 to q.

These sources are respectively connected to phase shifters b.i.j., which can introduce phase shifts, having quantified values, between their inputs and outputs. These phase shifters are supplied with ultra high-frequency power from a common main connection 2 through connections c.i. which distribute the ultra high frequency power between the various radiating sources.

The control of the value of the quantified phase shift introduced by the phase shifter b.i. is achieved by a phase computer 3 connected to the control input of the phase shifters by connections d.i. The computer 3 has inputs 30, 31, 32, 33 and 34. The input 30 is connected to the input 40 of a memory 4, whose output is connected to the input 34 of the computer 3.

The operation is as follows:

The computer 3 receives at its inputs 31, 32 and 33, respectively, the instantaneous, theoretical desired elevation 0 and bearing g values and the indication of the operating wavelength A. The memory 4 and the computer 3 are controlled simultaneously, for example by means of a program applied to the inputs 30 and 40, so that the computer receives at its input 34 the indication of the desired error sign for each phase shifter at the instant when the quantified phase shift, which this phase shifter must supply for a given elevation and bearing, is being calculated. In fact, the memory 4 stores the code according to which the direction of the phase error is determined for each radiating source. The memory 4 indicates therefore to the computer at the desired moment the direction in which it must apply the phase error. However, preferably, if the, quantification introduces only a small error (smaller than a quarter of one quantification step, for example), the computer will not change the direction of the error, even if this is indicated by the code. In fact, it is preferable, in this case, not to change the direction of the error, because its absolute value would become much greater (larger than three quarters of the quantification step, for example).

The stored code is such that the function direction of the phase error presents a substantially white spectrum.

By white spectrum is meant a spectrum similar to that of a white noise, i.e., a substantially uniform spectrum.

One thus obtains a reduction in the level of the secondary lobes by about 5 db.

In the case where the antenna comprises a mere alignment of radiating sources, a single code is suflicient. Where the antenna consists of an arrangement of radiating sources on a surface, it might be of greater interest to use two codes for the two main axes of the array.

Of course, the invention is not limited to the described embodiment and may be applied wherever one can act on the parameter direction of the systematic phase error due to the quantification.

What is claimed is:

1. An electronic scanning antenna comprising an array of a plurality of radiating sources, common energy supplying means for feeding said sources; a plurality of controlled phase-shifting means respectively coupled between said radiating sources and said common means for shifting the phase of said radiating sources by quantized amounts and having respective control inputs; computing means for computing the phase of each radiating source for a desired direction of the beam, said computing means having data inputs, a direction of the phase error input and a plurality of outputs respectively coupled to said control inputs; and memory means coupled to said last men- 4 computing means the direction of the phase error in the determination of each of said quantized amounts according to said code.

References Cited UNITED STATES PATENTS 3,083,360 3/1963 Welty et a1. 343--10O X 3,324,453 6/1967 Brightman 343l00 X 3,387,301 6/1968 Blass et a] 343-100 RODNEY D. BENNETT, JR., Primary Examiner T. H. TUBBESING, Assistant Examiner US. Cl. X.R.

tioned input for storing a code and for supplying to said 15 343 54 

